Direct radio frequency (RF) sampling with recursive filtering method

Abstract

A radio receiver 2000 with a sampling mixer 1100 for creating a discrete-time sample stream by directly sampling an RF current with history and rotating capacitors 1111 and 1112, wherein the accumulated charge on the rotating capacitors is read-out to produce a sample. The mixer provides immunity to noise glitches by predicting the occurrence of the glitch (or detecting a significant difference between observed and predicted samples) and creating corrected samples for the corrupted samples. These corrected samples can be created with special circuitry 1933 (digital) or in the mixer 1100 (analog).

Description

[0001]This application claims priority to provisional applications Ser. No. 60 / 312,602, filed Aug. 15, 2001, and Ser. No. 60 / 313,772, filed Aug. 20, 2001 and Ser. No. 60 / 348,902, filed Oct. 26, 2001. Each of these provisional applications is assigned to the assignee of this application and is also incorporated herein by reference as if each of the applications was reproduced in its entirety herein.FIELD OF THE INVENTION[0002]This invention relates generally to wireless communications systems, and particularly to direct sampling of radio frequency signals and filtering of same.BACKGROUND OF THE INVENTION[0003]Discrete-time radio frequency (RF) is a newly emerging field in wireless digital communications wherein analog RF signals that are transmitted over-the-air are directly sampled into a discrete-time sample stream suitable for digital signal processing. A typical wireless digital communications device would use analog filters, duplexers, mixers, analog-to-digital converters (ADC),...

AI Technical Summary

Benefits of technology

[0022]Additionally, use of a preferred embodiment of the present invention reduces the overall amount of hardware that needs to be integrated into an integrated circuit. By reducing the hardware requirements, it is possible to create a smaller radio transceiver. A smaller radio transceiver leads to a smaller, less expensive product.

[0023]Also, the use of a preferred embodiment of the present invention allows the sampling capacitor to be brought to a prespecified bias voltage while consuming only a small amount of power. This low power consumption increases battery life (or reduces the size of a power supply) and decreases heat dissipation concerns.

[0024]Additionally, use of a preferred embodiment of the present invention permits adjustments to be made to the amount of current used to bring the sampling capacitor to a prespecified bias voltage. For example, due to manufacturing (fabrication) variations, the actual value of the sampling capacitors may vary (sometimes significantly) from its nominal value. Therefore, a fixed current will place a bias voltage on the sampling capacitor that differs from the specified value. Use of a preferred embodiment of the present invention permits the charging current to be adjusted to place precisely the desired amount of bias voltage on the sampling capacitors.

[0025]Also, use of a preferred embodiment of the present invention reduces the overall noise injected into the system. The noise reduction is due to fact that each tim

Problems solved by technology

Unfortunately, analog circuit components, especially components such as capacitors, inductors, resistors, etc. necessary for the analog filters are difficult to integrate into an integrated circuit.

A reason for resetting the charge on the sampling capacitor is to prevent the excessive accumulation of charge during the sampling phase to saturate (or deplete) the charge storage capacity of the sampling capacitor, thus resulting in loss of information.

Once the sampling capacitor becomes saturated or depleted, information is lost.

A disadvantage of this technique is the amount of power consumed in bringing the sampling capacitor up to the bias voltage value.

Each time that the sampling capacitor is brought from zero volts to the bias voltage value, a significant amount of current is consumed.

This leads to the consumption of a considerable amount of power.

Therefore, the mixers can be quite complex, with four separate signal paths.

A significant disadvantage of having four separate signal paths in the mixer stems from the fact that each signal path requires a different clock.

However, the use of a different LO for each signal path can result in synchronization problems due to frequency differences in the signals generated by the different LOs, resulting in a degraded downconverted signal.

A major disadvantage in having separate clock generating hardware for each signal path is power consumption.

As expected, the clock generating hardware must also be clocked at high frequencies and hardware clocked at high frequencies consumes more power than hardware clocked at low frequencies.

Also for more complex clocking scheme

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